This invention relates to a vehicle driving device, and more specifically, to a lock-up clutch controlling device of a vehicle driving device having a fluid coupling equipped with a lock-up clutch.
A fluid coupling has been used as a power transmission coupling for ships, industrial machinery, and automobiles. A vehicle driving device with a fluid coupling is disclosed, for example, in Japanese Unexamined Patent Publication No. 1980-159360, and comprises an engine installed in a vehicle, the fluid coupling, a friction clutch, and a transmission which are disposed in series. The fluid coupling disposed in such a vehicle driving device can accommodate torque fluctuations and perform smooth power transmission. However, the fluid coupling inevitably involves slips between its input element (pump impeller) and its output element (turbine runner), thus resulting in a low efficiency of power transmission and a poor fuel economy. These slip-associated problems are true of a torque converter provided in an automatic transmission. A vehicle driving device equipped with a torque converter is provided with a lock-up clutch for directly connecting the input and output elements together under predetermined conditions, in order to solve the above-described problems.
In the vehicle driving device disclosed in Japanese Unexamined Patent Publication No. 1980-159360 that has the fluid coupling without a lock-up clutch, an unexpected clutch shock may occur when the friction clutch is engaged at completion of a gear change operation. Even in the vehicle driving device having the above-mentioned lock-up clutch provided in the fluid coupling, the clutch shock breaks out, if the lock-up clutch is not engaged during a gear change operation. Hereinbelow, the operating state, during gear change, of various members constituting the vehicle driving device provided with the fluid coupling will be described with reference to FIG. 9.
FIG. 9 shows an example of gear change for upshift, in which the horizontal axis shows an elapsed time during gear change. In FIG. 9, a solid line represents the clutch stroke of a friction clutch, a one-dot chain line represents the revolution speed of an engine, a two-dot chain line represents the clutch driven plate revolution speed of the friction clutch, and a dashed line represents the clutch drive plate revolution speed of the friction clutch. In FIG. 9, a gear change operation is started at a time point t1 while a vehicle is running. First of all, a driver begins to disengage the friction clutch at the time point t1, and nearly simultaneously releases an accelerator pedal. As a result, the engine revolution speed decreases as indicated by the one-dot chain line. When the driver performs an upshift operation for a transmission while the engine revolution speed is lowering, the revolution speed of a clutch driven plate indicated by the two-dot chain line is lowered to a revolution speed corresponding to the running speed of the vehicle not later than a time point t2 by the action of a synchromesh provided in the transmission, since the friction clutch is disengaged. When the operation for shifting up the transmission is completed, the driver starts engaging the friction clutch at a time point t3. At a time point t4, the friction clutch comes into a state of partial engagement. At a time point t5, the friction clutch is rapidly engaged based on a judgment that the revolution speed of the clutch driven plate and the engage revolution speed have agreed. However, a clutch drive plate of the friction clutch coupled to a turbine of a fluid coupling does not decrease in revolution speed in correspondence with the engine revolution speed, because of its own inertial force, although the engine revolution speed has lowered. Hence, a considerably great difference in revolution speed, (A), exists between the clutch drive plate and the clutch driven plate at the time point t4 when the above partial clutch engagement is achieved. Therefore, during the period from the time point t4, when the friction clutch becomes partially engaged, until the time point t5 when the friction clutch substantially becomes completely engaged, the rotation of the clutch drive plate rapidly decreases to eliminate the revolution speed difference (A). Consequently, an unexpected clutch shock develops.
The object of the present invention is to provide a lock-up clutch controlling device of a vehicle driving device equipped with a fluid coupling, the lock-up clutch controlling device being capable of preventing the occurrence of the aforementioned clutch shock at the time of engagement of a friction clutch at completion of a gear change operation.
To attain the above object, the present invention provides a lock-up clutch controlling device of a vehicle driving device, the vehicle driving device including an engine installed in a vehicle, a fluid coupling actuated by the engine, and a friction clutch disposed between the fluid coupling and a transmission, the fluid coupling having a lock-up clutch, the lock-up clutch controlling device comprising:
lock-up clutch actuating means for actuating the lock-up clutch;
gear change operation detecting means for detecting a gear change operation of the transmission; and
controlling means which, based on detection signals from the gear change operation detecting means, controls the lock-up clutch actuating means so as to engage the lock-up clutch during the gear change operation.
The gear change operation detecting means may comprise clutch detecting means for detecting an engagement state of the friction clutch, and vehicle speed detecting means for detecting a running speed of the vehicle; and
when the friction clutch is disengaged and the running speed of the vehicle is not less than a predetermined speed, based on detection signals from the clutch detecting means and the vehicle speed detecting means, the controlling means may judge that the gear change operation is being performed.
To attain the aforementioned object, the present invention also provides a lock-up clutch controlling device of a vehicle driving device, the vehicle driving device including an engine installed in a vehicle, a fluid coupling actuated by the engine, and a friction clutch disposed between the fluid coupling and a transmission, the fluid coupling having a lock-up clutch, the lock-up clutch controlling device comprising:
lock-up clutch actuating means for actuating the lock-up clutch;
gear change operation detecting means for detecting a gear change operation of the transmission;
clutch engagement amount detecting means for detecting an amount of engagement of the friction clutch; and
controlling means for controlling the lock-up clutch actuating means based on detection signals from the gear change operation detecting means and the clutch engagement amount detecting means; and wherein:
based on the detection signals from the gear change operation detecting means and the clutch engagement amount detecting means, the controlling means engages the lock-up clutch during the gear change operation, and disengages the lock-up clutch when the amount of engagement of the friction clutch has reached a predetermined amount.
The gear change operation detecting means may comprise the clutch engagement amount detecting means, and vehicle speed detecting means for detecting a running speed of the vehicle; and
when the friction clutch is disengaged and the running speed of the vehicle is not less than a predetermined speed, based on detection signals from the clutch engagement amount detecting means and the vehicle speed detecting means, the controlling means may judge that the gear change operation is being performed.
To attain the aforementioned object, the present invention further provides a lock-up clutch controlling device of a vehicle driving device, the vehicle driving device including an engine installed in a vehicle, a fluid coupling actuated by the engine, and a friction clutch disposed between the fluid coupling and a transmission, the fluid coupling having a lock-up clutch, the lock-up clutch controlling device comprising:
lock-up clutch actuating means for actuating the lock-up clutch;
gear change operation detecting means for detecting a gear change operation of the transmission;
engine revolution speed detecting means for detecting a revolution speed of the engine;
input shaft revolution speed detecting means for detecting a revolution speed of an input shaft of the transmission; and
controlling means for controlling the lock-up clutch actuating means based on detection signals from the gear change operation detecting means, the engine revolution speed detecting means, and the input shaft revolution speed detecting means; and wherein:
based on the detection signals from the gear change operation detecting means, the engine revolution speed detecting means, and the input shaft revolution speed detecting means, the controlling means engages the lock-up clutch during the gear change operation, and disengages the lock-up clutch when a difference between the revolution speed of the engine and the revolution speed of the input shaft of the transmission has reached a predetermined amount.
The gear change operation detecting means may comprise clutch detecting means for detecting an engagement state of the friction clutch, and vehicle speed detecting means for detecting a running speed of the vehicle; and
when the friction clutch is disengaged and the running speed of the vehicle is not less than a predetermined speed, based on detection signals from the clutch detecting means and the vehicle speed detecting means, the controlling means may judge that the gear change operation is being performed.